Bearing capacity of open-ended piles in sand

Abstract

The aim of this study is to evaluate the loading capacity of open ended piles in cohesionless soils by using PLAXIS. The simulation program PLAXIS uses finite element method to calculate load capacity and solve the problem. At the beginning of the study, the model for simulation was rough and less detailed. In the advancing steps, the model was changed and improved according to test results to be more realistic and correct. Axisymmetric model was used for this simulation. In the model, the parameters at pile surrounding and especially the pile toe were changed to understand the effect to pile capacity. Internal friction angle, modulus of elasticity, active lateral pressure K0 and the interval of K02 change rates were the selected parameters. At the end of the tests, the effect and the magnitude of the effects due to parameter changes were examined. A 15 meter open ended pile was modeled and the entire tests were conducted on the same type of pile to compare results easily. To model extra squeezing and probable “plugging” condition at the inner part of the pile, a special zone in this inner part with higher E values was created. One of the aims was to understand the contribution of this “plugging” zone to load capacity. After modeling was completed, the factor of safety values under various loads was calculated. To derive the ultimate load capacity under varying parameters, piles were loaded until collapsing will occur. Test results show that, the most effective parameter for load capacity in this kind of problem is the characteristics of soil at the pile toe and pile toe neighborhood. The increments or change of soil parameters in the inner side of the pile do not produce a remarkable effect on load capacity. That small changes in results may caused by the solution method of PLAXIS (Finite Element Method). Because the non-breaking and nontearing finite triangular elements of PLAXIS, producing a flawless simulation model is hard to apply.